A new class of high molecular weight organosilicon polymers which have excellent physical, thermal and electrical properties and outstanding resistance to water, and that can be used to prepare shaped articles is described in parent application Ser. Nos. 07/079,740 and 06/901,092. They are thermoset or thermoplastic organosilicon polymers comprising alternating polycyclic hydrocarbon residues and cyclic polysiloxanes or siloxysilane residues linked through carbon to silicon bonds.
Preferred organosilicon polymers are the reaction product of (a) a cyclic polysiloxane or a tetrahedral siloxysilane containing at least two hydrosilane groups and (b) a polycyclic polyene, wherein the ratio of carbon-carbon double bonds in the rings of (b) to hydrosilane groups in (a) is greater than 0.5:1 and up to 1.8:1 and at least one of the compounds (a) and (b) has more than two reactive sites.
U.S. patent application Ser. No. 07/079,740 also describes a method of preparing the organosilicon polymers according to the invention which is characterized in that it comprises reacting, in the presence of a platinum-containing catalyst, (a) a cyclic or tetrahedral polysiloxane containing at least two hydrosilane groups and (b) a polycyclic polyene, the ratio of carbon-carbon double bonds in (b) to hydrosilane groups in the rings of (a) being greater than 0.5:1 and up to 1.8:1 and at least one of the compounds (a) and (b) having more than two reactive sites, and subjecting said polymer to heat to drive the cross-linking to a maximum.